introduction to the immune system Flashcards
(26 cards)
What is Immunology?
Immunology is the study of our body’s sytems for preventing and treating diseases.
How is the Immune System organized?
Innate Immunity - and a second, more specific defence -
Adaptive Immunity. The adaptive immunity can be humoural (ie. B cells and antibodies) or it can be cellular (ie. T cells). White Blood Cells (WBCs) are key players in the immune system.
what are the components of innate immunity?
→physical barriers ( skin, mucosal surfaces)
→chemical barriers ( pH, secreted factors)
→phagocytes (monocytes/granulocytes/neutrophils)
→inflammation
→ acute phase response
→cytokines and chemokines
→complement
→natural killer cells
what is the inflammatory response triggered by?
→ the release of pro-inflammatory cytokines and chemokines at the site of infection
what is the purpose of the inflammatory response?
→localize and eliminate injurious agents and to remove damages tissue components
what occurs during the inflammatory response?
→enhanced permeability and extravasation
→neutrophil recruitment
→enhanced cell adhesion
→ enhanced clotting
what are cytokines and chemokines?
glycoprotein hormones that affect the immune response
what do cytokines do?
they act to modify the behavior of cells in the immune response
most of them are called interleukins
what do chemokines do?
act as chemotactic factors that create concentration gradients which attract or repel certain cell types to a site of infection or production
how do macrophages detect microbes?
→Macrophages have phagocytic receptors that bind microbes and their components.
→They detect substances that are usually presented on pathogens (non-self).
what are protein-associated molecular patterns PAMPs and give some examples?
→PAMPs are small molecular motifs conserved within a class of microbes.
→ glycans → lipopolysaccharides →bacterial flagellin → lipoteichoic acid → peptidoglycan →nucleic variants normally associated with viruses, such as double-stranded RNA
what are damage-associated molecular patterns (DAMPs) and give some examples
→DAMPs are molecules released by stressed cells undergoing necrosis.
→vary greatly depending on the type of cell and injured tissue.
→Some of these endogenous danger signals are proteins
→ heat-shock proteins and cytokines.
→Non-protein DAMPs include ATP, heparin sulfate and DNA.
what are pattern recognition receptors? (PRR) and what are they encoded by?
→host factors that specifically recognize a particular type of PAMP.
→ germ-line encoded.
what are the three types of PRR?
EXTRACELLULAR:
→they recognize PAMPs outside of a cell and trigger a coordinated response to the pathogen
INTRACELLULAR (CYTOPLASMIC):
→recognize PAMPs inside a cell and act to coordinate a response to the pathogen
SECRETED:
→act to tag circulation pathogens for elimination
how does interferon work?
→A virus infects a cell, which then becomes known as the primary infected cell.
→ virus will multiply inside the cell, and, after the cell dies, it will release the viral progeny.
→as the primary infected cell is dying, it releases interferons.
→interferons are picked up by other healthy cells, and they induce the transcription of >400 antiviral genes.
→ healthy cells in an antiviral state so viruses cannot affect them.
what is the ligand and outcome of lectin receptors?
LIGAND: terminal mannose, fucose
OUTCOME: phagocytosis
what is the ligand and outcome of scavenger receptors?
LIGAND: bacterial cell walls, modified low-density lipoproteins
OUTCOME: phagocytosis
what is the ligand and outcome of Toll like receptors?
LIGAND: lipopolysaccharides together with CD14 (LPS), lipoproteins, unmethylated CpG, flagellin, dsRNA and ssRNA (in endosomes)
OUTCOME: phagocytosis, inflammation,
what is the ligand and outcome of NOD like receptors?
LIGAND: peptidoglycan from Gram-positive and negative bacteria, some viral DNA and
RNA
OUTCOME: inflammation, cytokine release (IL-1, IL-8)
what is the ligand and outcome of RIG-like receptors?
LIGAND: dsRNA and 5’-triphosphate RNA
OUTCOME: type I interferon production
what are complement proteins?
→A system of secreted proteins made in the liver that recognise PAMPs on the surface of microbes and ‘decorate’ or ‘tag’ them.
→The microbes are then cleared by phagocytosis, “opsonised” (C3 sticks to pathogen membranes) or they have holes punched in them.
what are the three pathways of activating complement proteins?
→recognition of LPS and other PAMPs by the C1q component of the ‘classical’ pathway
→ non-host glycosylation is recognised by MBP (mannan/mannose-binding protein) and other lectins to activate the ‘lectin’ pathway
→ membranes that are recognised as “non-self” activate the ‘alternative’ pathway Complement activation involves a proteolytic cascade.
what is the structure of natural killer cells?
→they are large granular lymphocytes.
→they make up about 4% of WBCs.
→ lymphocyte-like, but larger with a granular cytoplasm.
→ kill certain tumour cells and virally-infected cells.
→ Target cell destruction is caused by the cytotoxic molecules called granzymes and perforins.
how are natural killer cells activated?
→Natural killer (NK) cells are activated by loss-of-self.
→An NK cell has an MHC receptor on its surface.
→With an uninfected cell, it will present the ligand for the MHC receptor, stimulating an inhibitory signal that stops the NK cell from killing it.
→ with an infected cell, they do not present this ligand, so the inhibitory signal is not presented
→releases perforin and cytotoxic granules into the infected cell or engages the cell’s death receptors.
